The invention relates to the control of motors. More particularly, the present invention relates to the control of motor torque of a motor.
In centrifuge systems, a motor is used to drive or rotate a centrifuge rotor. The centrifuge rotor top speed is limited by the torque that the motor can produce and the windage or drag torque produced as the centrifuige rotor rotates in air. In order to prevent or reduce the possibility of centrifuge rotor accidents, the drag or windage torque required to drive the centrifuge rotor equals the motor torque and the centrifuge rotor cannot be driven faster. The maximum kinetic energy of the centrifuge rotor is calculated at this point. Thus, the centrifuge containment system is then designed to properly contain a failure of the centrifuge rotor at this point of maximum kinetic energy.
Improving motor technology allows for increased motor torque which would allow the centrifuge rotor to be driven to a higher windage limited speed. At this higher windage limited speed the kinetic energy of the centrifuge rotor may exceed the proven energy containment limit of the centrifuge exposing the user to a dangerous situation. This could lead to centrifuge rotor failure and the possibility of centrifuge rotor accidents.
Accordingly, it is desirable to provide an invention that will avoid centrifuge rotor failure that would exceed the proven containment of the centrifuge.
The foregoing needs are met, to a great extent, by the present invention, wherein in one aspect an apparatus is provided that in one embodiment includes a control unit that adjusts the motor torque to equal the windage torque limit of a centrifuge rotor there by preventing the centrifuge rotor from being driven to a higher speed that would exceed the proven containment to the centrifuge.
In accordance with another embodiment of the invention, a method of controlling the torque of a motor includes the steps of driving a centrifuge rotor connected to the motor; increasing a motor torque of the motor to a specified level; and adjusting the motor torque to equal the windage torque of a centrifuge rotor and thereby limit the kinetic energy of said rotor.
The motor torque can be adjusted so that it does not exceed a specified windage torque limit and in some cases be decreased so that the lower motor torque results in a lower windage torque limit and thereby a lower kinetic energy.
The method can further include detecting revolutions per minute of the centrifuge rotor. The motor torque can be increased based on the detected revolutions per minute or otherwise adjusted. In some cases at a predetermined revolutions per minute the motor can be decreased to a constant torque over a range of detected revolutions per minute and then increased or further decreased.
In another embodiment of the invention, a system for controlling the torque of a motor includes a means for driving a centrifuge rotor connected to the motor; a means for increasing a motor torque of the motor to a specified level; and a means for adjusting the motor torque according to a predetermined windage torque limit of the centrifuge rotor or another predetermined torque range.
The means for adjusting the motor torque can adjust the motor torque so that it does not exceed a predetermined centrifuge rotor windage torque limit. In some cases the motor torque can be decreased so that the centrifuge rotor windage limit is lowered thereby decreasing the kinetic energy of the centrifuge rotor.
The system can also include a means for detecting revolutions per minute of the centrifuge rotor. The motor torque in some instances can be increased based on the detected revolutions per minute. In other embodiments the motor torque can be adjusted based on the detected revolutions per minute. For instance, in an alternate embodiment of the invention the motor torque can be decreased to a constant torque over a range of detected revolutions per minute and then increased or further decreased at subsequent higher revolutions per minute.
Another embodiment of the invention is a device that controls the torque of a motor, or a controller. The device includes a shaft connected to the motor. A centrifuge rotor is coupled to the shaft. The motor drives the shaft thereby moving the centrifuge rotor. A control unit, or controller, is in communication with the motor. The control unit increases a motor torque of the motor to a specified level, and adjusts the motor torque according to a predetermined torque curve.
The control unit can adjust the motor torque so that it does not exceed a predetermined windage torque limit of the selected centrifuge rotor. The control unit can also decrease the motor torque so that it limits a centrifuge rotor top speed to limit the maximum kinetic energy or the centrifuge rotor.
The control unit can adjust the motor torque to lower the motor torque over a specified speed range to prevent large centrifuge rotors, with high windage torque, from exceeding this speed range. Smaller centrifuge rotors with lower windage torque can be accelerated through this reduced motor torque speed range. Once past this rpm range of lowered motor torque, motor torque can then be increased to enhance the acceleration performance of the smaller centrifuge rotors.
A detector in communication with the control unit can also be provided. The detector can be used to determine revolutions per minute of the centrifuge rotor and decrease the motor torque based on revolutions per minute detected by said detector. In some instances the control unit can increase the motor torque based on revolutions per minute determined by the detector.
The control unit in one embodiment of the invention can determine revolutions per minute of the centrifuge rotor, and adjust the motor torque based on the detected revolutions per minute. The motor torque can in some cases be decreased to a constant torque over a range of detected revolutions per minute. Or can adjust the motor torque output to any type of mathematical curve such as a constant horsepower curve.
In an alternate embodiment of the invention, a method for controlling the torque of a motor includes the steps of driving a centrifuge rotor connected to the motor; increasing a motor torque of the motor to a specified level; detecting revolutions per minute of the centrifuge rotor; adjusting the motor torque based on detected revolutions per minute; decreasing the motor torque to a constant torque over a range of revolutions per minute; and increasing the motor torque when the detected revolutions per minute are outside of the range.
There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein maybe better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, arc for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.